BMC Microbiology BioMed Central Review Protein secretion systems in bacterial-host associations, and their description in the Gene Ontology

Virginia Bioinformatics Institute, Virginia Polytechnic Institute and State University, Blacksburg, VA 24061, USA.
BMC Microbiology (Impact Factor: 2.73). 02/2009; 9 Suppl 1(Suppl 1):S2. DOI: 10.1186/1471-2180-9-S1-S2
Source: PubMed


Protein secretion plays a central role in modulating the interactions of bacteria with their environments. This is particularly the case when symbiotic bacteria (whether pathogenic, commensal or mutualistic) are interacting with larger host organisms. In the case of Gram-negative bacteria, secretion requires translocation across the outer as well as the inner membrane, and a diversity of molecular machines have been elaborated for this purpose. A number of secreted proteins are destined to enter the host cell (effectors and toxins), and thus several secretion systems include apparatus to translocate proteins across the plasma membrane of the host also. The Plant-Associated Microbe Gene Ontology (PAMGO) Consortium has been developing standardized terms for describing biological processes and cellular components that play important roles in the interactions of microbes with plant and animal hosts, including the processes of bacterial secretion. Here we survey bacterial secretion systems known to modulate interactions with host organisms and describe Gene Ontology terms useful for describing the components and functions of these systems, and for capturing the similarities among the diverse systems.

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    • "The causative agent of human tuberculosis disease, Mycobacterium tuberculosis, uses novel mechanisms for evasion of host responses for its intracellular survival (Berry et al., 2013; Cambier et al., 2014). Often bacterial pathogenicity depends upon the ability to stash virulence factors which can be either displayed at the bacterial cell surface or secreted into extracellular milieu in addition to direct injection into the target cell (Tseng et al., 2009). In bacteria, protein export across the cytoplasmic membrane represents the first step in the delivery of proteins to the cell envelope or extracellular space. "
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    ABSTRACT: The mycobacterial tlyA gene product, Rv1694 (MtbTlyA), has been annotated as “hemolysin” which was re-annotated as 2′-O rRNA methyl transferase. In order to function as a hemolysin, it must reach the extracellular milieu with the help of signal sequence(s) and/or transmembrane segment(s). However, the MtbTlyA neither has classical signals sequences that signify general/Sec/Tat pathways nor transmembrane segments. Interestingly, the tlyA gene appears to be restricted to pathogenic strains such as H37Rv, M. marinum, M. leprae, than M. smegmatis, M. vaccae, M. kansasii etc., which highlights the need for a detailed investigation to understand its functions. In this study, we have provided several evidences which highlight the presence of TlyA on the surface of M. marinum (native host) and upon expression in M. smegmatis (surrogate host) and E. coli (heterologous host). The TlyA was visualized at the bacterial-surface by confocal microscopy and accessible to Proteinase K. In addition, sub-cellular fractionation has revealed the presence of TlyA in the membrane fractions and this sequestration is not dependent on TatA, TatC or SecA2 pathways. As a consequence of expression, the recombinant bacteria exhibit distinct hemolysis. Interestingly, the MtbTlyA was also detected in both membrane vesicles secreted by M. smegmatis and outer membrane vesicles secreted by E. coli. Our experimental evidences unambiguously confirm that the mycobacterial TlyA can reach the extra cellular milieu without any signal sequence. Hence, the localization of TlyA class of proteins at the bacterial surface may highlight the existence of non-classical bacterial secretion mechanisms.
    Frontiers in Cellular and Infection Microbiology 07/2015; 5(60). DOI:10.3389/fcimb.2015.00060 · 3.72 Impact Factor
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    • "While growing either in a natural ecosystem or artificial conditions, bacteria secrete intracellular products into their extracellular milieu (Tseng et al. 2009). Secretory products are not only involved in bacterial social behavior , usually referred to as quorum sensing (Molloy 2010) but also in pathogenicity (Lee and Schneewind 2001) and inter-kingdom communication (Hughes and Sperandio 2008; Shen et al. 2012; Furusawa et al. 2013). "
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    MicrobiologyOpen 01/2015; 4(2). DOI:10.1002/mbo3.235 · 2.21 Impact Factor
    • "Secretion systems pathways (type IV and VI) were discovered in Gram-negative bacteria. They facilitate the transport of DNA, proteins or molecules from the bacterial cytoplasm directly into prokaryote cells (Tseng et al., 2009). The type IV secretion system is the unique type secretion system discovered in Gram-positive bacteria (Melville and Craig, 2013). "
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    ABSTRACT: Listeria monocytogenes is a pathogenic Gram positive bacterium and the etiologic agent of listeriosis, a severe food-borne disease. Lactococcus piscium CNCM I-4031 has the capacity to prevent the growth of L. monocytogenes in contaminated peeled and cooked shrimp. To investigate the inhibititory mechanism, a chemically defined medium (MSMA) based on shrimp composition and reproducing the inhibition observed in shrimp was developed. In co-culture at 26 °C, L. monocytogenes was reduced by 3-4 log CFU g−1 after 24 h. We have demonstrated that the inhibition was not due to secretion of extracellular antimicrobial compounds as bacteriocins, organic acids and hydrogen peroxide. Global metabolomic fingerprints of these strains in pure culture were assessed by liquid chromatography coupled with high resolution mass spectrometry. Consumption of glucose, amino-acids, vitamins, nitrogen bases, iron and magnesium was measured and competition for some molecules could be hypothesized. However, after 24 h of co-culture, when inhibition of L. monocytogenes occurred, supplementation of the medium with these compounds did not restore its growth. The inhibition was observed in co-culture but not in diffusion chamber when species were separated by a filter membrane. Taken together, these data indicate that the inhibition mechanism of L. monocytogenes by L. piscium is cell-to-cell contact-dependent.
    Food Microbiology 01/2015; DOI:10.1016/ · 3.33 Impact Factor
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